From bd69a255fd195a4c52563f09a367b56f54373de9 Mon Sep 17 00:00:00 2001
From: lion <chenxin619315@gmail.com>
Date: Tue, 21 Oct 2025 10:28:56 +0800
Subject: [PATCH] return empty string for empty match

---
 binding/java/ReadMe.md                                 | 10 +++++++++-
 binding/java/pom.xml                                   |  2 +-
 .../main/java/org/lionsoul/ip2region/xdb/Searcher.java |  8 ++++----
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/binding/java/ReadMe.md b/binding/java/ReadMe.md
index cda493e..efb8e7a 100644
--- a/binding/java/ReadMe.md
+++ b/binding/java/ReadMe.md
@@ -7,10 +7,18 @@
 <dependency>
     <groupId>org.lionsoul</groupId>
     <artifactId>ip2region</artifactId>
-    <version>3.1.0</version>
+    <version>3.1.1</version>
 </dependency>
 ```
 
+### 关于查询结果
+定位信息查询 API 的原型为：
+```java
+String search(String ipStr) throw Exception;
+String search(byte[] ip) throw Exception;
+```
+查询出错会抛出异常，如果查询成功会返回字符串的 `region` 信息，如果指定的 ip 查询不到会返回空字符串 `""`，这对于自定义数据或者数据不完整的情况会出现。
+
 ### 关于 IPv4 和 IPv6
 该 xdb 查询客户端实现同时支持对 IPv4 和 IPv6 的查询，使用方式如下：
 ```java
diff --git a/binding/java/pom.xml b/binding/java/pom.xml
index dea3fc7..295628b 100644
--- a/binding/java/pom.xml
+++ b/binding/java/pom.xml
@@ -4,7 +4,7 @@
 
     <groupId>org.lionsoul</groupId>
     <artifactId>ip2region</artifactId>
-    <version>3.1.0</version>
+    <version>3.1.1</version>
     <packaging>jar</packaging>
 
     <name>ip2region</name>
diff --git a/binding/java/src/main/java/org/lionsoul/ip2region/xdb/Searcher.java b/binding/java/src/main/java/org/lionsoul/ip2region/xdb/Searcher.java
index 974da13..68264a8 100644
--- a/binding/java/src/main/java/org/lionsoul/ip2region/xdb/Searcher.java
+++ b/binding/java/src/main/java/org/lionsoul/ip2region/xdb/Searcher.java
@@ -124,8 +124,8 @@ public class Searcher {
         final int bytes = ip.length, dBytes = ip.length << 1;
         final int segIndexSize = version.segmentIndexSize;
         final byte[] buff = new byte[segIndexSize];
-        int dataLen = -1;
-        long dataPtr = -1, l = 0, h = (ePtr - sPtr) / segIndexSize;
+        int dataLen = 0;
+        long dataPtr = 0, l = 0, h = (ePtr - sPtr) / segIndexSize;
         while (l <= h) {
             long m = (l + h) >> 1;
             long p = sPtr + m * segIndexSize;
@@ -145,8 +145,8 @@ public class Searcher {
 
         // empty match interception
         // System.out.printf("dataLen: %d, dataPtr: %d\n", dataLen, dataPtr);
-        if (dataPtr < 0) {
-            return null;
+        if (dataLen == 0) {
+            return "";
         }
 
         // load and return the region data